High voltage rectifier



Sept. 16, 1941. I c VOGEL 2,256,330

HIGH VOLTAGE RECTIFIER Filed June 29, 1940 F191. VT 1 1 I z i i I I 3 I] r V k IZ a H z 8 if f l a fli a 9 I 3nv entor Cllfll'ZSf Va ez,

Gttomeg Patented Sept. 16, 1941 HIGH VOLTAGE RECTIFIER Charles P. Vogel, Millburn, N. .L, assignor to Radio Corporation of America, a corporation of Delae ware Application June 29, 1940, Serial No. 343,073

4 Claims.

My invention relates to electron discharge devices, particularly to high voltage rectifiers.

The anode-cathode space of a rectifier is usually connected in series with a condenser of a filter and the high voltage secondary winding of a power transformer. On one-half cycle, when rectifying in the forward direction with the anode positive with respect to the cathode, th condenser charges. On the other half cycle, the anode is swung negative by the transformer winding, while the cathode is held positive by its connected condenser plate. The high positive potential on the cathode and high negative potential on the anode are additive and cause electron emission from the surface of the anode, particularly from anode areas upon which active cathode metal, such as barium, may have condensed during activation or use of the cathode. This emission from the anode may cause uncontrollable bombardment and heating of the envelope and considerable loss of energy, with a reduction of the D. C. output voltage and may cause radio frequency interference due to unstable bulb charges if the tube is operated near a radio receiver.

The object of my invention is a high voltage rectifier tube in which emission from the anode is prevented from causing efi'ects harmful to the envelope.

The characteristic features of my invention are defined in the appended claims and preferred embodiments thereof are described in the following specification and shown in the accompanying drawing in which Figure 1 is an elevational view, particularly in section, of a high voltage rectifier constructed according to my invention, Figure 2 is a view of the cathode assembly of Figure 1 looking in the direction of th arrows 22 in Figure 1, Figure 3 is a sectional view of the cathode assembly taken on lines 3-3 in Figure 1, Figure 4 is a side elevational view, partly in section, of another high voltage rectifier embodying my invention, and Figure5 is a section on line 5-5 of Figure 4.

The conventional glass envelope l with reentrant stem and press 2 encloses a cup-shaped anode 3 supported by a lead-in conductor sealed into the upper end of the envelope. Cathode 4 in this particular embodiment of my rectifier comprises two V-shaped filaments connected at their ends to lead-in conductors 5 in the press and supported at their bights on two insulated hooks 6 carried on a central supporting stud I embedded in the press. Alternatively, the oathode may comprise a single helical coil coaxial with the anode and supported at its ends on the leadin conductors 5. A metal cylinder 8 is mounted coaxialwith the anode and is supported on studs 9, and is mechanically joined at its upper end to the filament conductors by an insulating disc I 0. One of the supporting studs 9 for the cylinder 8 is extended through the press in a lead-in conductor so that the potential of cylinder 8 may be externally established. Extending outwardly from the side of the cylinder is a cup-shaped shield II with its rim overlying the lower rim of the anode so that no points on the electron collecting surface of the anode is in line of sight of the envelope wall.

Any active metals that may be liberated from the surface of cathode 4 during operation or during activation of the cathode in manufacture, fiow outwardly from the cathode and condense on all of the surface of the anode within view of the cathode. Electrons are emitted from this activated surface of the anode when the anode becomes highly negative with respect to the cathode and the electron velocity and reverse current density becomes high when the peak inverse voltage becomes several thousand volts, as required in many cathode ray tube circuits. Reverse current electrons, however, are effectively prevented from bombarding the envelope by shield ll extending over the end of the anode. All points on the electron collecting surface of the anode facing upon the cathode are out of line sight of the envelope wall.

The complete shielding of the envelope from all electron bombardment from the anode is effected in my novel rectifier by a structurein which the anode is supported free of the cathode and cathode lead-in structure. The complete absence of inter-electrode insulating spacers and the unobstructed space between the anode and cathode structure permits operation of my novel rectifier at voltages which, in the conventional rectifiers, would cause arcing and sputtering between electrodes, and destruction of spacers.

Electron shielding and inter-electrode insulation in my rectifier have been found to be so effective that an anode only -750 inch in diameter and coaxial with a filamentary cathode may be operated at a peak inverse voltage of 60,000 volts without arcing and without appreciable heating of the envelope.

A directly heated ribbon type getter l2 with a coating compound of reducible active metals is connected at its ends, in the example shown, between one leg of the filament and the cylinder 8. Active metals evolved from getter [2 are effectively confined to the inner wall of cylinder 8 and are prevented from condensing on the envelope Wall. If desired the lower end of cylinder 8 may be closed by a second disc fitted over the lead-in conductors and crimped into the lower end of the cylinder. This construction permits the existence of active getter material within the tube, and at the same time permits the glass envelope to be free of getter deposit, thus permitting the complete utilization of the insulating path of the envelope. It further eliminates the losses which may occur in the glass due to contamination of the glass surface by the getter, and permits oper ating this rectifier tube at frequencies of the.

order of 500,000 cycles per second.

The cathode of my novel rectifier may, if desired, be of the indirectly heated type as shown in Figure 4. The lower end of the cathode sleeved passes through the spacer l and is attached as by spot welding, to two parallel truss bars 13, which in turn are attached at their ends to pillars l4 staked into the spacer on opposite sides of the sleeve. The pillars may comprise elongated hollow rivets beaded on either side of the insulating disc I0 and riveted in an upstanding position to rigidly hold the truss bars and the cathode sleeve. The spacer I0 may be of insulation or metal. If the spacer is of insulation, the sleeve should be electrically connected to supporting studs 9 and cylinder 8 by a short connector.

My improved high voltage rectifier prevents arcing between electrodes, prevents bombardment of the envelope with the electrons and is simple in construction and inexpensive to manufacture.

I claim:

1. A rectifier comprising an envelope, a cupshaped anode supported at one end of said envelope, a cathode in said anode supported on lead-in conductors at the other end of said envelope, a first metal cylinder surrounding said lead-in conductors coaxial with said anode and smaller in diameter than the anode, a getter comprising a reducible compound of active metals in said first cylinder, and a second cylinder larger in diameter than the anode supported on said first cylinder, said cylinders and anode being coaxial, with the larger cylinder telcscoped over but only slightly overlying the rim of the anode.

2. A rectifier comprising an envelope, an open ended cup-shaped anode supported by a lead-in wire sealed in one end of said envelope, lead-in conductors sealed in the other end of said envelope with unobstructed space between the anode and conductors, a cathode in the anode supported on the ends of two of said conductors, a metal cylinder surrounding the cathode conductors coaxial with said anode, a ribbon type getter connected between another two of said conductors in said cylinder, and a cup-shaped shield supported solely on said cylinder with the rim of the shield overlying the rim of said anode.

3. A high voltage rectifier comprising an envelope, an open ended cup-shaped anode supported on a lead-in wire sealed in one end of said envelope, a tubular cathode sleeve coaxial with said anode, means for supporting said sleeve comprising a disc normal to the axis of the anode with a central opening through which said sleeve extends, a truss bar fixed to and parallel with said spacer fastened to said sleeve at a point removed from said opening.

4. A high voltage rectifier comprising an envelope, a cathode in said envelope supported by one end of said envelope, a cup-shaped anode in said envelope supported by the other end of the envelope and free of and in spaced relation with said cathode and enclosing said cathode with unobstructed evacuated space between the anode and the cathode and the anode leads, and a cupshaped shield connected to the cathode and solely supported upon the cathode leads, said shield being coaxial with and telescoped between the wall of the envelope and the rim of the anode with all points on the surface of the anode within line of sight of the cathode shielded from the envelope.

CHARLES P. VOGEL. 

